# http_proxy=http://192.168.0.104:7890
# https_proxy=http://192.168.0.104:7890

Sys.setenv("http_proxy"="http://192.168.0.104:7890")
Sys.setenv("https_proxy"="http://192.168.0.104:7890")

url <- "www.google.com"

httr::GET(url)
